Dolby Laboratories DP570 D.6 Parameter Definitions

92 Dolby® DP570 Multichannel Audio Tool User’s Manual
A Guide to Dolby Metadata Parameter Definitions
streamtoeitheradownstreamdecoderoranintegratedamplifierwithDolbyDigital
decoding.
Ineachofthesedevices,theanalogstereooutputisoneoftwodifferentstereodownmixes.
Onetypeisastereo‐compatibleDolbySurrounddownmix,ofthemultichannelsource
programthatissuitableforDolbySurroundProLogic®decoding.Thiskindofdownmix
isalsocalledProLogicorLefttotal/Righttotal(Lt/Rt).Theothertypeisasimplestereo
representation(calledLeftonly/Rightonly,orLo/Ro)suitableforplaybackonastereohi‐fi
oronheadphones,andfromwhichamonosignalisderivedforuseonanRF/Antenna
output.ThedifferencebetweenthedownmixesishowtheSurroundchannelsarehandled.
TheLt/RtdownmixsumstheSurroundchannelsandaddsthem,in‐phasetotheLeft
channelandout‐of‐phasetotheRightchannel.ThisallowsaDolbySurroundProLogic
decodertoreconstructtheL/C/R/SchannelsforaProLogichometheater.TheLo/Ro
downmixaddstheLeftandRightSurroundchannelsdiscretelytotheLeftandRight
speakerchannels,respectively.Thispreservesthestereoseparationforstereo‐only
monitoringandproducesamono‐compatiblesignal.Inalldownmixes,theLFEchannelis
notincluded.
Onmosthomeequipment,theconsumercanusetheproduct’suserinterfacetochoosethe
appropriatestereooutputforhisplaybacksystem.Themonosignalfeedingthe
RF/AntennaoutputisusuallyderivedfromtheLo/Rodownmix.
ThereareseparatemetadataparametersthatgoverntheLo/RoandLt/Rtdownmixes.
Certainmetadataparametersallowtheengineertoselecthowthestereodownmixis
constructedandwhichstereoanalogsignalispreferred,butLt/Rtisthedefaultselection
inallconsumerdecoders.SeeParameterDefinitionsonpage 92forthedefinitionof
individualparameters.
Duringdownmixing,aswehaveseen,theadjustmentofDynamicRangeControl
parametersislimited.Broadlyspeaking,thestereooutputsusetheLinemodecompression
profilewhilethemonosignalusesRFmodecompression.Aswithdynamicrangecontrol,
downmixingisultimatelydependentuponeachconsumer’suniquelistening
environment.
Whiletheengineermustoptimizethemultichannelmixforreproductioninanideal
listeningenvironment,itisalsoimportanttopreviewthemixindownmixingconditions
toensurecompatibilitywithdifferentplaybacksystemswhenselectingthedownmixing
metadataparameters.ThesepreviewscanbeachievedinrealtimeusingtheDP570
MultichannelAudioTool.
D.6 Parameter Definitions
Thissectionexplainsbothprofessionalandconsumermetadataparametersingreater
detail.
Metadataparametersinclude:
•Universalparameters
•ExtendedBitstreamInformation(ExtendedBSI)parameters
ExtendedBSIparametersareactiveonlywhenboththeproducerchoosestousethemand
theconsumer’sdecoderiscapableofreadingthem.Alldecoderscansuccessfullydecodea